As this type of ion beam irradiation device, there is one provided with an ion source that extracts an ion beam that has a rectangular sectional surface with a long side size that is longer than a substrate and a short side size that is shorter than the substrate, a reciprocating mechanism that reciprocates the substrate in a short side direction of the ion beam such that the substrate travels across an ion beam irradiation region, and a rotating mechanism that causes the substrate to rotate in a stepwise manner about a central portion when the substrate is outside the ion beam irradiation region, as disclosed in Patent Document 1.
However, since the substrate is caused to move to the outside of the ion beam irradiation region every time the substrate is reciprocated, a substrate processing efficiency deteriorates, and it takes a long time to perform the substrate processing.
In addition, since the substrate is caused to rotate outside the ion beam irradiation region, it is necessary to cause the substrate to move to the outside of the ion beam irradiation region every time the substrate is caused to rotate, this leads to an increase in the number of times the substrate is reciprocated, and this also leads to an increase in time required to perform the substrate processing.
Further, if the substrate is caused to move (scan) to the outside of the irradiation region again from the outside of the ion beam irradiation region across the irradiation region, an effective beam current density in the irradiation of the substrate decreases.
Specifically, the effective beam current density ie per scanning becomes ie=I/(L×D), as illustrated in FIG. 7. Here, I is a beam current with a length, which corresponds to a substrate diameter length, in the ion beam, L is a substrate scanning length (the amount of movement of the substrate), D is a substrate diameter, and BW is a width of the ion beam. Also, since the substrate travels across the ion beam irradiation region, L>BW+D is satisfied. In a case in which L does not meet this condition, it is difficult to obtain uniformity in the substrate processing. As is clear from the aforementioned equation, the effective beam current density ie decreases as the scanning length L increases. Also, since a substrate processing time is proportional to the effective beam current density ie, a long scanning length L is disadvantageous.